There are various types of sounds emitted adjacent to a vehicle driving on a road. If a driver is an aged person having at least partially impaired hearing or a person who has a bad sense of sound direction, he or she would be insensitive to such sounds and unable to produce a response to a particular sound made by a warning horn, a siren, or the like, which he or she should pay attention to. In addition, since in-vehicle technology providing sound insulation has been developed, it is likely that even a driver having great hearing could not correctly hear a noise/sound emitted outside a vehicle. The driver's inability to sense such sounds may put the driver's safety at risk, notably in cases in which the driver does not keep his/her eyes forward when he/she listens to a specific sound from the rear of the vehicle.
Accordingly, it might be beneficial to provide information about a particular sound, such as what kind of sounds exists adjacent to a vehicle, which direction a sound comes from, and the like, to a driver without disruptions to driving safety. However, if a driver receives information about sounds generated by his or her own vehicle, such as sibilant voices from tires, driving safety may be compromised as a result of information overload and notifications about such sound information should not be generated or delivered.